1 Field of the Invention
The present invention relates to an attachment element and, in particular, to a rock anchor for use in mining and/or tunnel driving and including a boring head and a hollow cylindrical receiving body. The receiving body has, at its end, facing in a setting direction of the attachment element, a recess for receiving the boring head and at its opposite end, an engagement element. In the receiving body, there is provided one or multi-component mortar mass, preferably packed in a bag. The attachment element is provided with at least one outlet opening through which the mortar mass is squeezed out under pressure applied by piston. Between the mortar mass and the at least one outlet opening, a channel section is provided.
2. Description of the Prior Art
Rock anchors are used for stabilization of walls of hollow spaces such as tunnels, galleries, and the like and, in particular, for connecting rock regions adjacent to a wall with each other. In many cases, the regions which are located immediately adjacent to the wall and mechanical characteristics of which, in particular the load-carrying capacity, are reduced as a result of formation of hollow spaces, are connected to more remote, undamaged regions. The wall, in this regard, means the ceiling and side walls of a hollow space and also its bottom.
As a rock anchor, e.g. a so-called tubular anchor, which is formed of a tubular element provided, at its setting direction end, with a boring head and at its opposite end, with engagement means, is often used. At least one outlet channel extends through the boring head. The setting process of the known tubular anchor is effected into two steps. In the first step, the anchor is drilled, with an available boring tool, into the ground, in particular, rock. The degraded and comminuted stone, which is produced at the bore-side end of the anchor by the boring head, is removed through the outlet openings and the space between the bore wall and the outer circumference of the tubular anchor. In the second step, a mortar mass is introduced into the tubular member through the anchor end remote from the setting direction end of the anchor, and is pressed into the direction toward the bore by a piston and with the plunger of squeezing device. The mortar mass, which is located in the tubular anchor, is introduced into the bore from the tubular anchor through the outlet opening in the boring head. The mortar mass is distributed along the space or gap between the bore wall and the outer circumference of the tubular anchor. In this way, the known tubular anchor is anchored and/or secured.
The introduction of the mortar mass into the tubular anchor after the boring step is associated with additional, in particular timewise expenses, on one hand, and on the other hand, can be effected, dependent on the site conditions, only conditionally and often only using very expensive technical measures. Sometimes, the anchoring is not of adequate quality, which can lead, in the worst case, to replacement of the installed anchor.
German Publication DE-100 17 750 A1 discloses a rock anchor containing to-be-squeezed out mortar mass. The tubular anchor is provided, at its setting direction end, with outlet openings. Between the multi-component mass and the outlet openings, there is provided a mixer, so that the mortar mass, which is subject to pressure by a piston, is adequately mixed before it leaves the tubular body.
The drawback of the anchor disclosed in DE-100 17 750 A1 consists in that in order to insure removal of the comminuted stone which is produced by the boring head, the so-called drillings, a sufficiently large gap should be provided between the bore wall and the outer wall of the tubular body. To this end, the bits of the boring head should project sufficiently far beyond the cross-section of the tubular body. To insure anchoring of this rock anchor in a borehole, a large amount of mostly expensive mortar mass should be used, on one hand, and, on the other hand, high requirements are placed on the material characteristics of the mortar mass, e.g., its contraction, shrinkage, during hardening. With an increased thickness of the mortar mass layer, the possibility of failure of contraction during hardening increases.
Accordingly, the object of the present invention is to provide an attachment element, in particular for use in mining and/or tunnel driving, with which the mortar mass is contained in the attachment element during the entire setting process.
Another object of the present invention is to provide an attachment element with which the amount of mortar mass necessary to insure a reliable anchoring is reduced to a minimum.